Engine oils are finished crankcase lubricants intended for use in automobile engines and diesel engines and consist of two general components, namely, a base stock or base oil (one base stock or a blend of base stocks) and additives. Base oil is the major constituent in these finished lubricants and contributes significantly to the properties of the engine oil. In general, a few lubricating base oils are used to manufacture a variety of engine oils by varying the mixtures of individual lubricating base oils and individual additives.
Governing organizations (e.g., the American Petroleum Institute) help to define the specifications for engine oils. Increasingly, the specifications for engine oils are calling for products with excellent low temperature properties and high oxidation stability. Currently, only a small fraction of the base oils blended into engine oils are able to meet the most stringent of the demanding engine oil specifications. Currently, formulators are using a range of base stocks spanning the range including Group I, II, III, IV, and V to formulate their products.
Base oils are generally recovered from the higher boiling fractions recovered from a vacuum distillation operation. They may be prepared from either petroleum-derived or from syncrude-derived feed stocks. Additives are chemicals which are added to improve certain properties in the finished lubricant so that it meets the minimum performance standards for the grade of the finished lubricant. For example, additives added to the engine oils may be used to improve stability of the lubricant, increase its viscosity, raise the viscosity index, and control deposits. Additives are expensive and may cause miscibility problems in the finished lubricant. For these reasons, it is generally desirable to lower the additive content of the engine oils to the minimum amount necessary to meet the appropriate requirements.
Formulations are undergoing changes driven by need for increased quality. Changes are seen in engine oils with need for excellent low temperature properties and oxidation stability and these changes continue as new engine oils categories are being developed. Industrial oils are also being pressed for improved quality in oxidation stability, cleanliness, interfacial properties, and deposit control.
Generally, feedstocks suitable for formation of lubricant base oils correspond to vacuum gas oil boiling range feeds from a vacuum distillation. In some situations, however, a deasphalted oil formed by propane desaphalting of a vacuum resid has been conventionally used for additional lubricant base stock production. Deasphalted oils can potentially be suitable for production of heavier base stocks, such as bright stocks. However, the severity of propane deasphalting required in order to make a suitable feed for lubricant base stock production typically results in a yield of only about 30 wt % deasphalted oil relative to the vacuum resid feed.
Despite advances in lubricating base oils and lubricant oil formulation technology, there exists a need for formulated oils that can be formed from non-traditional and/or challenged feeds while still providing desirable characteristics and performance in lubricant applications (for example, for engine oils and industrial oils).
U.S. Pat. No. 3,414,506 describes methods for making lubricating oils by hydrotreating pentane-alcohol-deasphalted short residue. The methods include performing deasphalting on a vacuum resid fraction with a deasphalting solvent comprising a mixture of an alkane, such as pentane, and one or more short chain alcohols, such as methanol and isopropyl alcohol. The deasphalted oil is then hydrotreated, followed by solvent extraction to perform sufficient VI uplift to form lubricating oils.
U.S. Pat. No. 7,776,206 describes methods for catalytically processing resids and/or deasphalted oils to form bright stock. A resid-derived stream, such as a deasphalted oil, is hydroprocessed to reduce the sulfur content to less than 1 wt % and reduce the nitrogen content to less than 0.5 wt %. The hydroprocessed stream is then fractionated to form a heavier fraction and a lighter fraction at a cut point between 1150° F.-1300° F. (620° C.-705° C.). The lighter fraction is then catalytically processed in various manners to form a bright stock.